Actuating devices are typically provided for engaging and disengaging gears in motor vehicle transmissions. Known actuating devices for classic manual transmissions are typically provided with a shift linkage. The drive energy, which is required for engaging and disengaging gears, is essentially completely applied by the driver in this case, who introduces it manually into a shift lever coupled to the shift linkage. Furthermore, actuating devices are known which have an electric motor and/or an arrangement of electric motors, using which gears are engaged and disengaged. Actuating devices of this type are known to be used—in diverse embodiments—in, for example, auto shift transmissions (AST), uninterrupted shift transmissions (UST), electrical shift transmissions (EST), or in parallel shift transmissions (PST) and/or twin-clutch transmissions (TCT).
The actuating device, including the electric motor(s), is also referred to as an actuator in the designs of the latter type. The actuator typically is coupled in the motor vehicle to an internal gear shifter, which has shift rails and/or shift forks and/or shift sleeves, for example, and may load this internal gear shifter. An electronic control unit is known to be provided to activate the electric motors. This electronic control unit activates the electric motors, which is typically performed as a function of diverse characteristic values, in particular operating characteristic values of the motor vehicle, such as engine speed and/or engine torque or the like. In this case, an operating element may be provided, via which the driver may select diverse modes (e.g., forward (D), reverse (R), park (P), shift up (+), shift down (−)), as a function of which the electronic control unit activates the electric motors.
Furthermore, it is known that actuators of this type have a first electric motor, which causes selection movements, and a second electric motor, different therefrom, which generates the shift movements. In addition, it is known that the output and/or drive shafts of these two electric motors are each coupled via suitable mechanical units to a selector shaft in such a way that this selector shaft may be pivoted around its longitudinal axis using one electric motor and may be moved translationally in the direction of its longitudinal axis using the other of the two electric motors. The shifting is caused in this case through a corresponding pivot of this selector shaft and the selection is caused in this case by a corresponding translational movement of the selector shaft, or vice versa.
In addition, the applicant has developed actuating devices and/or actuators for motor vehicle transmissions, which manage with only one electric motor, i.e., in which the selection and the shifting may be caused using precisely one electric motor. Exemplary embodiments of this type are disclosed in DE 10 2004 038 955 of the applicant.
For example, in the embodiments of the type explained in FIGS. 9a through 24 of DE 10 2004 038 955 a problem may occur—at least under unfavorable conditions—which is to be explained in the following on the basis of FIGS. 6a and 6b. 
FIGS. 6a and 6b show a detail of an exemplary 1-motor transmission actuator and/or an exemplary actuating device for a motor vehicle transmission, which may otherwise be implemented, for example, like the embodiment according to FIGS. 9a through 24 of DE 10 2004 038 955.
FIGS. 6a and 6b particularly show a threaded spindle 330, and a spindle nut 332 and a first movably positioned component 376, which is particularly an eccentric 376. The first component 376 is positioned so it is axially fixed and rotationally movable and is referred to in the following as the eccentric 376. A wedge gearing connection is provided between the eccentric 376 and the spindle nut 332, which is schematically indicated in the cutaway area of FIG. 6a by the arrow 491 and which particularly acts as a rotational carrier unit. The spindle nut 332 has an internal thread, which engages in an external thread of the threaded spindle 330. The corresponding threaded connection is indicated in the cutaway area of FIG. 6a by the arrow 490.
The threaded spindle 330 is positioned so it is rotationally movable and axially fixed and may be alternately driven by an electric motor (not shown) in opposite rotational directions. The spindle nut 332 is positioned so it is essentially rotationally movable in the axial position, which is shown in FIGS. 6a and 6b. This axial position may be approached in that the threaded spindle 330 and/or the electric motor connected thereto rotates and/or drives in such a way that the spindle nut 332 travels in the direction of the eccentric 376. The corresponding rotational direction of the spindle nut 332 and/or the electric motor corresponds to the selection direction of this spindle nut 332 and/or this electric motor. In the axial position of the spindle nut 332 shown in FIGS. 6a and 6b, the spindle nut 332 stops axially on a stop which, in the event of a movement of the threaded spindle 330 and/or the electric motor in the selection direction, blocks the axial mobility of the spindle nut 332. In the event of continued movement of the threaded spindle 330 and/or the electric motor in the selection direction in particular, the threaded spindle 330, the spindle nut 332, and the eccentric 376 rotate and/or move jointly. This may be exploited to select a gear.
The selection direction of the threaded spindle 330 and/or the rotational movement of the threaded spindle 330 in the selection direction and/or the selection movement of the threaded spindle 330 is schematically indicated in FIG. 6a by the arrow 492. The (rotational) movement of the eccentric 376 triggered in this case by and/or upon the coupling of threaded spindle 330, spindle nut 332, and eccentric 376 is schematically indicated in FIG. 6a by the arrow 494.
Now, however, if in and/or from this state, in which the spindle nut 332 and the eccentric 376 are rotationally carried by the threaded spindle 330 (particularly in the selection direction), the threaded spindle 330 and/or the electric motor is suddenly stopped—which is schematically indicated by the symbol 496 in FIG. 6b—the eccentric 376 rotates further and/or its inertial mass causes the eccentric to be moved further. In this way (because of this), the spindle nut 332 travels along the threaded spindle 330, particularly in the direction directed away from the stop and/or the spindle nut 332. This may particularly be attributed to the inertial mass and/or energy and/or the mass inertia torque of the eccentric 376 and/or the corresponding influence of any components coupled thereto and carried therewith (cf. arrow 493 in FIG. 6b). Under unfavorable conditions, this may possibly result in the eccentric 376 being moved into a (selection) position, from which a shift may be made into an undesired gear. Furthermore, this may result in the position of the spindle nut 332 and/or the eccentric 376 and/or the first component no longer being able to be concluded sufficiently correctly from the position information provided by the controller, so that under unfavorable conditions incorrect operations may result. This is because, in units of this type, the position information may be ascertained via an incremental sensor provided on the electric motor and/or its output shaft and provided to the controller.
Thus, particularly because of the lack of a “fixed” connection between the eccentric 376 and connected mass inertias and the threaded spindle 330 and/or the motor, it is made more difficult or impossible to stop the mechanism during braking-particularly without disadvantages. This would be desirable particularly in regard to short shifting times, however.
It is to be noted that the problem discussed may also possibly occur—at least partially—if the threaded spindle 330 is driven in the direction opposite the selection direction, particularly if the spindle nut 332 is not supported in relation to the housing or is not supported rotationally fixed in relation to the housing.